Changes in chemical composition of some oils extracted from seeds roasted at different temperatures

Abstract

Oil seeds are commonly used in cooking, frying and as salad oil and have commercial and economic importance. Since the seeds are roasted before pressing of the oil, changes occur in their composition; thus it is crucial to modify roasting process to minimise adverse effects. This study reflects the effects of different roasting temperatures (90, 150 and 210 °C for 10 min. in conventional oven) on the oil constituents and some chemical properties of oils from the seeds of sesame, sunflower, soybean, flaxseed and poppy along with comparison to those of unroasted corresponding seed oils. Lipids from roasted seeds of sesame, flax and soybean exhibited relatively higher viscosity and free fatty acids, than lipids from unroasted seeds. With an increase in roasting temperatures the colour of the oils were slightly darker even though the changes were not significant in most cases. The content of α-and γ-tocopherols in oils (except soybean oil) gradually decreased as roasting temperature increased. β-tocopherol was higher in the oils of roasted seeds, while the amount of δ-tocopherol showed different trends with roasting depending on the type of seeds. For sesame and poppy oils, after roasting at 210 °C, stearic and oleic acids showed higher percentages when compared to the levels in oils roasted at 90 and 150 °C.

Effects of Roasting Temperature and Time on the Chemical Composition of Argan Oil

“…The studies on the effects of roasting on the chemical composition and the oxidative stability of argan oil are not numerous. In addition, the temperature used by the authors remains relatively low (110°C) [ 11 , 36 , 37 ] compared to works done on other oilseeds [ 6 , 7 , 29 , 38 ], but also with regard to the temperatures applied for the traditional extraction of argan oil intended for commerce or for a familiar use. Indeed, the extraction of argan oil is mainly done using the artisanal process, especially in rural areas of southern Morocco.…”

“…As regards the effect of roasting on the content of tocopherols which represent the major antioxidants of vegetable oils, the data from the literature are inconsistent. Depending on the nature and variety of oilseeds, roasting may lead to a decrease [ 5 – 7 ] or an increase in tocopherols level in oil [ 8 – 10 ]. Since tocopherols are thermosensitive, their final concentration in the oil will depend essentially on the temperature and the duration of the roasting.…”

Quality improvement of oil extracted from flaxseeds (Linum usitatissimum L.) incorporated with olive leaves by cold press

“…However, the obtained results showed that the rate of polyunsaturated fatty acid oxidation was less in the oil extracted from the flaxseeds with leaves, particularly blanched leaves, at a level of 5%–7.5% compared with the control sample (Table 3 ). It has been reported that flaxseed oil is sensitive to oxidation, and its 18:3 and 18:2 content has been decreased during processing and the storage (Simsek et al., 2015 ). The obtained results in this study agree with the previously published data (Jung et al., 2021 ; Mikołajczak & Tańska, 2022 ).…”

The Effect of Extraction by Pressing at Different Temperatures on Sesame Oil Quality Characteristics

“…Different pre-treatments such as moisture adjustment, roasting, ohmic heating and microwaving can be used to enhance the oil extraction yield and also to improve the extracted oil quality [10][11][12][13]. It is also possible to change the temperature during oil extraction from nuts and oilseeds by pressing and to use higher temperatures up to 200 • C [14].…”